Method and apparatus for compacting isostatically metal particles into solid form

ABSTRACT

Metal particles are confined in a tube of ductile material capable of collapsing against the particle butyl of resisting penetration by the particles. The tube is encased in a buffer material capable of compression through its thickness, and the buffer material is enclosed in a liquid-impervious, flexible container. The assembly is evacuated an immersed in a liquid, and the liquid then is pressurized to collapse the assembly and compact the particles into coherent, solid form.

Jan. 5, 1971 BACKER. ETAL 3,551,946

METHOD AND APPARATUS FOR COMPACTING ISOSTA'IICALLY METAL PARTICLES INTO SOLID FORM Filed Aug. 26, 1968 54 50 42 48 4& g? 4 0 Leo E.Backer Daniel G.Lorzg V BY IN ENTORS United States Patent O 3,551,946 METHOD AND APPARATUS FOR COMPACTING ISOSTATICALLY METAL PARTICLES INTO SOLID FORM Leo E. Backer and Daniel G. Long, Albany, Oreg., as-

signors to Wah Chang Albany Corporation, Albany, reg., a corporation of Oregon Filed Aug. 26, 1968, Ser. No. 755,196 Int. Cl. B29g 1/00 US. Cl. 18-5 Claims ABSTRACT OF THE DISCLOSURE Metal particles are confined in a tube of ductile material capable of collapsing against the particles but of resisting penetration by the particles. The tube is encased in a buffer material capable of compression through its thickness, and the buffer material is enclosed in a liquidimpervious, flexible container. The assembly is evacuated and immersed in a liquid, and the liquid then is pressurized to collapse the assembly and compact the particles into a coherent, solid form.

BACKGROUND OF THE INVENTION This invention relates to the compaction of metal particles to coherent, solid shapes, and more particularly to the isostatic compaction of coarse, irregular shaped particles of metal into bars, cylinders and other coherent, solid forms.

In the purification of metals such as zirconium, titanium, columbium and many others, it is conventional practice to prepare the metal in the form of an elongated rod which may be utilized as an electrode in an arc furnace, or as a melt stock in an electron beam furnace. Such an elongated rod has been formed heretofore by either of two methods. One of said methods involves placing the metal particles in a die and forcing a plunger into the die with suflicient pressure to form a solid compact of the metal. A plurality of the compacts then are Welded together to form an elongated rod. This method is time consuming and therefore costly, and it has the further disadvantage of contaminating the metal with the weld stock.

The second method employed heretofore involves the reduction of the metal substantially to powder form which is placed in a rubber or other liquid-impervious, flexible container. Air is evacuated from the container and the latter then is immersed in a liquid contained in a pressure vessel. The vessel then is pressurized, whereupon the container is caused to collapse and the powder is compacted to solid form. This method involves the costly step of reducing the metal to powder form in order to prevent rupture of the rubber container.

SUMMARY OF THE INVENTION In its basic concept the present invention involves the confinement of metal particles of random sizes and shapes in a container having an inner section of ductile material capable of collapsing against the particles but resisting penetration by the particles, an intermediate section of buffer material capable of compression through its thickness, and an outer section of liquid-impervious, flexible material. The container is evacuated and immersed in a liquid which then is pressurized to effect collapsing of the container and compaction of the particles into a coherent, solid form.

It is by virtue of the foregoing basic concept that the principal objective of the present invention is achieved, namely to overcome the disadvantages of prior methods, as enumerated hereinbefore.

The foregoing and other objects and advantages of the 3,551,946 Patented Jan. 5, 1971 present invention will appear from the following detailed description taken in connection with the accompanying drawing of the preferred embodiment of the apparatus.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary, foreshortened vertical elevation of apparatus illustrating the method of the present invention and embodying the structural features of the present invention, parts being broken away to disclose details of internal construction.

FIG. 2 is a foreshortened vertical section of liquid pressurizing means for compressing the assembly of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing there is illustrated a multiplicity of metal particles 10 of random shape and size, to be compacted into a coherent, solid mass. The metal particles may be of zirconium, columbium, hafnium, titanium, or any other metal desired to be compacted, and they may be in the form of metal sponge, chips, turnings, chunks and other random shapes and sizes.

The metal particles are confined within a tube 12 of ductile material capable of collapsing against the particles but of resisting penetration by the particles. Various types of materials may be used for the tube. For example, zirconium, aluminum and other metal foils have the foregoing capabilities. However, they tend to stick to the irregular surface of the compacted mass and thus are difiicult to remove. However, there are many instances in which such surface contamination of the compacted mass is not objectionable.

Red belting material, comprising a lamination of fabric and rubber, has the foregoing capabilities, but also tends to adhere slightly to the surface of the compacted mass. However, there are many applications in which such surface contamination is not objectionable. Stainless steel wire belting has the foregoing capabilities and is readily removable from the surface of the compacted mass.

It has been found that conventional black iron stovepipe material is most admirably suited for the purpose of the tube, since it possesses the foregoing capabilities, releases readily from the surface of the compacted mass, and is very inexpensive. Accordingly, it is the preferred material.

Prior to deposit of the metal particles in the tube, the bottom end of the latter is closed by a plate 14 of similar stovepipe material. As illustrated in the drawing, this bottom plate rests freely upon a bottom annular flange 16 formed by turning inward the lower portion of the tube. After the metal particles have been deposited in the tube, a top plate 18 of similar stovepipe material is placed over the contents and retained against upward displacement by the overlying flange 20 formed by turning inward the upper portion of the tube.

The filled tube then is encased in a buffer material capable of compression through its thickness. In the embodiment illustrated, the buffer material comprises a length of cardboard tubing 22, and end plates 24 and 26 of cardboard overlying the opposite ends of the tube. Although other materials, such as red belting are capable of compression through their thickness and thus are suitable buffer materials, cardboard is preferred for its low cost.

If desired, an outer buffer sheath 28 of rubber coated fabric, or other suitably flexible and compressible material may surround the cardboard tubing.

The foregoing assembly of tube and buflFer materials then is fitted with end caps 30 and 32 of rubber, or other suitable flexible material. In the preferred embodiment illustrated the upper cap 30 is spaced from the bufler material by one or more spacer strips 34 of rubber, or other flexible material, to facilitate evacuation of the assembly, as described hereinafter.

The foregoing capped assembly then is placed within a container 36 of liquid-impervious, flexible material, such as rubber, polyethylene, or other suitably flexible plastic. One or more spacer strips 38 of flexible material then are placed between the upper cap 30 and the outer container, after which the upper end of the outer container is sealed by a cap 40 of rubber, or other suitably flexible material. This cap has an upturned rim 42 which abuts the inner surface of the outer container and is sealed thereto by means of the inner and outer metal clamp rings 44 and 46, respectively. To facilitate removal of the rings, inner and outer bands 48 and 50 of rubber are interposed between the rings and the adjacent surfaces of the cap flange and outer container, respectively.

The sealing cap is provided with a flexible tube 52 integral therewith. The inner end of the tube passageway communicates with the interior of the outer container and the outer end thereof is connected to a shutoff valve 54 which communicates through a length of tubing 56 to a vacuum pump (not shown).

With the components assembled as described, air is evacuated from the interior by manipulating the valve 54 to connect the interior of the container with the vacuum pump. The evacuated assembly then is immersed in water or other substantially non-compressible liquid contained in a pressure vessel. The vessel then is sealed and pressurized sufficiently to effect collapsing of the container assembly and compaction of the metal particles into a coherent, solid mass. After compaction, the fluid pressure is relieved, the vessel opened and the collapsed container assembly removed. The outer container is opened by re moval of the clamping rings and cap. These may be reused indefinitely. The assembly of cardboard tubing, stovepipe tube and the compacted metal then is removed from the outer container and the cardboard tubing and stovepipe tube are stripped from the compacted mass. These components generally are not reusable.

The following examples illustrate the method and apparatus of the present invention:

EXAMPLE I 75 pounds of zirconium sponge particles in the form of very hard, large, angular chunks, many of which were too large to pass through .41" screen material, was filled into a standard diameter black stovepipe having a thickness of 0.149". A 5" diameter cardboard tubing was placed around the stovepipe and closed with /1" thick rubber end plugs. Natural rubber caps and spacer strips were installed, after which the assembly was placed in a natural rubber bag of /a thickness. After evacuation, the assembly was immersed in Water contained in a modified vertical 8" naval gun (FIG. 2) provided with a hydraulic pumping system 62 and removably closed by its breech block 64. The water was pressurized to 25,000 p.s.i. Upon removal of the assembly and stripping of the cardboard and stovepipe tubings from the metal, the latter was found to have been compacted to a coherent, solid mass, by shrinkage of about 17%.

EXAMPLE II 295 pounds of minus zirconium sponge and three zirconium ingots of 72 pounds each were filled into a 11.5" diameter stovepipe surrounded with a cardboard tubing and placed within a 14" diameter natural rubber bag, in manner similar to the procedure illustrated in Example I. After evacuation for minutes, this assembly was immersed in water contained in a modified l6 naval gun and pressurized to 25,000 p.s.i. Pressurization took about one hour. The reulting compacted metal mass was found to have shrunk in height from 28" to 25.6" and in diameter from 13.1" to 11.5". The compact was well shaped, with no visible area denoting the presence of the zirconium ingots within the compact.

From the foregoing it will be appreciated that the method and apparatus of the present invention afiords economical means by which to form coherent, solid compacts of metal particles of random size and shapes, thereby overcoming the disadavantages of prior procedures as enumerated hereinbefore.

Having now described our invention and the manner in which it may be used, we claim:

1. Apparatus for compacting isostatically metal particles of random shapes and sizes into a solid form, comprising (a) a hollow tube adapted to be filled with particles to compacted,

(b) bottom closure means for closing the bottom end of the tube,

(c) top closure means for closing the top end of the tube,

(d) the tube and closure means being of expandable ductile material capable of collapsing against the particles under hydrostatic pressure without fracture and being removable from about the compacted form,

(e) buffer means surrounding the tube and being of expendable material capable of compression through its thickness,

(f) container means enclosing the butter means and tube and being of liquidimpervious, flexible material capable of collapsing under hydrostatic pressure,

(g) means communicating with the container means for evacuating the latter, and

(h) pressure vessel means adapted to receive the container means removably therein and including means for pressurizing liquid therein for collapsing the container, bufier means and tube for isostatically compacting the metal particles into a solid form.

2. The apparatus of claim 1 wherein the hollow tube is of black iron stovepipe material.

3. The apparatus of claim 1 wherein the hollow tube is of stainless steel wire cloth material.

4. The apparatus of claim 1 wherein the hollow tube is of rubber belting material.

5. The apparatus of claim 1 wherein the hollow tube is of zirconium foil.

6. The apparatus of claim 1 wherein the buffer means is of cardboard.

7. The apparatus of claim 1 wherein the buffer means is of rubber belting.

8. The apparatus of claim 1 wherein the container means comprises a rubber bag having an open end, and a rubber cap releasably sealing said open end.

9. The apparatus of claim 8 wherein the evacuating means comprises passageway means through the cap for evacuating the bag, and valve means releasably closing said passageway means.

10. The method of compacting isostatically metal particles of random shapes and sizes into a solid form, comprising (a) enclosing said particles in a hollow tube made of an expendable ductile material capable of collapsing against the particles under hydrostatic pressure without fracture and being removable from about the compacted form,

(b) encasing the tube in an expendable buffer material capable of compression through its thickness,

(c) enclosing the encased tube in a container of liquidimpervious, flexible material capable of collapsing under hydrostatic pressure,

(d) evacuating the container,

(e) immersing the evacuated container in a liquid,

(f) pressurizing the liquid to collapse the container, buffer material and tube and compact the particles into a solid form,

(g) reducing said pressure to atmosphere,

(h) removing the container from the liquid,

5 6 (i) removing the encased tube from the container, and 3,249,964 5/ 1966 Shaler 185 (j) stripping the bufifer material and tube from the 3,346,914 10/1967 Sandstrom et a1. 18-5 compacted form of particles. 3,419,935 1/ 1969 Pfelier et a1. 185 3,462,797 8/1969 Asbury 1834 References Cited 3,464,249 9/1969 Klein 72-56 UNITED STATES PATENTS WILLIAM S. LAWSON, Primary Examiner Huber.

Luebkeman 18-5 1 XR Swed 26484 Bergmann. 10 18-34; 26484, 111, 313

Simons 264--84X 

